Self-propelled hydrofoil devices are known in the art and include those disclosed in U.S. Pat. No. 7,021,232 to Chen (the inventor herein), which is hereby incorporated by reference, and the “Trampofoil” device disclosed in Swedish Design Patent no. 98-0088.
While these patents further the self-propelled hydrofoil art, they are disadvantageous for one or more reasons. For example, the device of Chen '232 has a bi-partite steering structure in which the upper and lower parts of the steering shaft are joined in a spring-biased pivoting arrangement. This arrangement is disadvantageous in that the spring mechanism and related coupling components constitute additional mechanical devices that increase the possibility of mechanical failure. Furthermore, they add to the cost and complexity of the steering shaft and its manufacturing process because they are additional parts that need to be sources and assembled within it.
A need exists for a self-propelled hydrofoil device having a steering shaft with a limited number of components (thereby increasing its useful life) that provides sufficient flexibility for effective movement of the drive foil yet with sufficient stability for steering.
The Trampofoil device is disadvantageous, among other reasons, in that the steering shaft, along its length from the handle to the front foil, is formed of a flexible material. While the flexibility of this shaft is beneficial in achieving the undulating tilt of the drive foil that serves to drive the hydrofoil device, the flexibility is too great laterally and causes the hydrofoil device to be both difficult to steer and unstable. Furthermore, the steering shaft of the Trampofoil is substantially linear and does not provide a sufficient angle between the top section and bottom sections to achieve ready bending of the steering shaft. A need thus exists for a steering shaft that is flexible for drive foil operation, yet sufficient stable for steering. A need also exists for such a steering shaft that has a sufficient angle between the top and bottom sections so that force from a downward thrust on the top section is transferred to the bottom section in a manner that readily bends the lower section to assist in drive foil positioning.
Prior art self-propelled hydrofoil devices are also disadvantageous in that they have limited buoyancy, which makes starting them difficult and increases their drag when pulled through water (for example, to pull them back to a dock for starting). Their buoyancy is limited to the scant amount of air trapped within the typically aluminum frame, foil, and other components.
A need exists for a self-propelled hydrofoil device having a steering shaft with a limited number of components (thereby increasing its useful life) that provides sufficient flexibility for effective movement of the drive foil yet with sufficient stability for steering.
A need also exists for a self-propelled hydrofoil device with greater buoyancy, to enhance restart and reduce drag, among other reasons.